linux-kernel - Re: dm-zoned: free dmz->ddev array in dmz_put_zoned

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Message-ID: <ZQsxvY12z+/yYcR6@redhat.com>
Date:   Wed, 20 Sep 2023 13:54:05 -0400
From:   Mike Snitzer <snitzer@...nel.org>
To:     Fedor Pchelkin <pchelkin@...ras.ru>
Cc:     Hannes Reinecke <hare@...e.de>, Alasdair Kergon <agk@...hat.com>,
        dm-devel@...hat.com, linux-kernel@...r.kernel.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        lvc-project@...uxtesting.org, stable@...r.kernel.org
Subject: Re: dm-zoned: free dmz->ddev array in dmz_put_zoned_device

On Wed, Sep 20 2023 at 10:35P -0400,
Fedor Pchelkin <pchelkin@...ras.ru> wrote:

> On 23/09/20 04:06PM, Hannes Reinecke wrote:
> > On 9/20/23 12:51, Fedor Pchelkin wrote:
> > > Commit 4dba12881f88 ("dm zoned: support arbitrary number of devices")
> > > made the pointers to additional zoned devices to be stored in a
> > > dynamically allocated dmz->ddev array. However, this array is not freed.
> > > 
> > > Free it when cleaning up zoned device information inside
> > > dmz_put_zoned_device(). Assigning NULL to dmz->ddev elements doesn't make
> > > sense there as they are not supposed to be reused later and the whole dmz
> > > target structure is being cleaned anyway.
> > > 
> > > Found by Linux Verification Center (linuxtesting.org).
> > > 
> > > Fixes: 4dba12881f88 ("dm zoned: support arbitrary number of devices")
> > > Cc: stable@...r.kernel.org
> > > Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>
> > > ---
> > >   drivers/md/dm-zoned-target.c | 8 +++-----
> > >   1 file changed, 3 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/drivers/md/dm-zoned-target.c b/drivers/md/dm-zoned-target.c
> > > index ad8e670a2f9b..e25cd9db6275 100644
> > > --- a/drivers/md/dm-zoned-target.c
> > > +++ b/drivers/md/dm-zoned-target.c
> > > @@ -753,12 +753,10 @@ static void dmz_put_zoned_device(struct dm_target *ti)
> > >   	struct dmz_target *dmz = ti->private;
> > >   	int i;
> > > -	for (i = 0; i < dmz->nr_ddevs; i++) {
> > > -		if (dmz->ddev[i]) {
> > > +	for (i = 0; i < dmz->nr_ddevs; i++)
> > > +		if (dmz->ddev[i])
> > >   			dm_put_device(ti, dmz->ddev[i]);
> > > -			dmz->ddev[i] = NULL;
> > > -		}
> > > -	}
> > > +	kfree(dmz->ddev);
> > >   }
> > >   static int dmz_fixup_devices(struct dm_target *ti)
> > 
> > Hmm. I'm not that happy with it; dmz_put_zoned_device() is using dm_target
> > as an argument, whereas all of the functions surrounding the call sites is
> > using the dmz_target directly.
> > 
> > Mind to modify the function to use 'struct dmz_target' as an argument?
> 
> dm_target is required inside dmz_put_zoned_device() for dm_put_device()
> calls. I can't see a way for referencing it via dmz_target. Do you mean
> passing additional second argument like
>   dmz_put_zoned_device(struct dmz_target *dmz, struct dm_target *ti) ?

No, what you did is fine.  Not sure what Hannes is saying given only
passing dm_target has symmetry with dm_get_zoned_device (and
dmz_fixup_devices).

> BTW, I also think it can be renamed to dmz_put_zoned_devices().

I've renamed like you suggested and added a newline to
dmz_put_zoned_devices() and staged this fix in linux-next for
upstream inclusion before 6.6 final releases.

Mike